Carburetor having fuel and air flow control means



CARBUREIOR HAVING FUEL AND AIR FLOW CONTROL MEANS Filed June,l7, 1965 Oct. 18, 1966 D. o. STOLTMAN 2 Sheets-Sheet l I N VENTUR. 00/70/0' [2 .S?0/%/770/2 A TTOHNE Y 1966 D. D. STOLTMAN 3,279,767

' CARBURETOR HAVING FUEL AND AIR FLOW CONTROL MEANS Filed June 17, 1965 2 Sheets-Sheet 2 E ,0 'b p j N Z? 5 T r 17 g/ I! 6.? Z2 M 2 F A 12' w Z IN VEN TOR.

BY Uma/a U Sb/zzmzz ATTORNEY United States Patent 3,279,767 CARBURETOR HAVING FUEL AND AIR FLOW CONTROL MEANS Donald D. Stoltman, Henrietta, N.Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 17, 1965, Ser. No. 464,806 3 Claims. (Cl. 261-23) This invention relates to internal combustion engine fuel systems and more particularly relates to means in such systems for measuring the rate of air flow to the engine and for controlling fuel flow in accordance therewith.

Although air valve controlled fuel systems are not in common use at the present time, it is well-known that air fiow may be measured by an air valve which is responsive to the volume of air flowing through the air inlet to the engine, The air valve may be connected to a fuel metering valve whereby fuel flow to the engine will be regulated in accordance with air flow and thus a proper mixture of air and fuel may be delivered to the engine. This invention, directed to such an air valve controlled engine fuel system, provides improved operating mechanism through which an air valve controls a fuel metering valve.

This improved mechanism permits an air valve to control fuel metering for both economy and power operation of an engine. To accomplish this, a metering cam has been developed which is positioned by the air valve and which has both economy and power scheduling portions. Fuel metering rods are controlled by a cam follower biased against the power scheduling portion of the cam so that air-fuel mixtures suitable for power operation is obtained. To obtain air-fuel mixtures for economy operation, means responsive to engine vacuum overcome the bias on the cam follower. The follower is then positioned by the economy scheduling portion of the cam, and lean air-fuel mixtures are delivered to the engine.

The details as well as other objects and advantages of this invention appear in the following description as well as in the drawings in which:

FIGURE 1 is a side elevational view of a carburetor showing by hidden lines the mixture conduits and the choke, throttle, and air valves which control the conduits;

FIGURE 2 is a top plan view of the carburetor of FIGURE 1 additionally illustrating by hidden lines the fuel bowl outline;

FIGURE 3 is a sectional view through one of the carburetor mixture conduits, along line 33 of FIGURE 2, illustrating the connection of the air valves to a damping mechanism;

FIGURE 4 is a sectional view along line 4-4 of FIG- URE 2 illustrating the return spring which biases the air valves to a closed position;

FIGURE 5 is a sectional view along line 55 of FIGURE 2 illustrating the metering cam and operating linkage which control the fuel inlet valves; and

FIGURE 6 is a sectional view along line 66 of FIGURE 2 illustrating the air valve damping piston, the fuel metering valves, and the fuel passages from the fuel bowl to the secondary mixture conduits.

Referring now to FIGURES 1 and 2, a four-barrel carburetor 10 includes a pair of primary mixture conduits 12 and a pair of secondary mixture conduits 14. The outlets from the mixture conduits are controlled in the customary manner by pairs of primary and secondary throttle valves 16 and 18, respectively. A choke valve 20 in the inlet to the primary mixture conduits 12 is controlled by a conventional automatic choke mechanism (not shown).

A pair of air valves 22 are secured in the inlets to the secondary mixture conduits 14 upon an air valve shaft 24 which extends through both conduits 14. Air valves 22 are unbalanced so as to be opened by air flow through mixture conduits 14. As shown in FIGURE 4, one end of shaft 24 carries a pin 26 around which is looped a spring 28. Spring 28 is secured about a pin 30 attached to the carburetor 10 and thus biases air valve shaft 24 in a clockwise direction as viewed in FIGURE 4. As air valves 22 are opened by air flow and shaft 24 rotates in a counterclockwise direction, the loop in the spring 28 slides along pin 26 to tailor the return force upon the air valve shaft 24 and air valves 22 in a desired manner.

As shown in FIGURE 3, a damping piston 32 is connected through a plunger 34 to a lever 36 Which is pivotally secured to the carburetor 10. A link 38 con: nects one of the air valves 22 with lever 36 so that as air valves-22 open, damping piston 32 is raised. Damping piston 32 is located in a cylinder 40 which, as shown in FIGURE 6, connects through a slot 42 with the carburetor fuel bowl 44. As damping piston 32 is pulled upwardly, the opening movement of air valves 22 will be retarded to prevent undue leaning of the air-fuel mixture.

A shoulder 45 on plunger 34 engages the top of piston 32 during closing movement of air valves 22 to force piston 32 down into cylinder 40. When damping piston 32 is lowered a valve 46 located within piston 32 is opened by plunger 34 so that fuel within cylinder 40 may pass upwardly through piston 32 to allow rapid closing movement of air valve 22. Piston 32 will then be ready to damp subsequent opening movement of the air valves.

A stop member 50 on lever 36' is located in the path of the one air valve 22 to prevent movement offairvvalves 22 beyond a wide open position.

Referring now to FIGURES 2 and 6, fuel from fuel bowl 44 passes through the secondary metering orifices 52 into passages 54 which in turn lead to the secondary main wells 56. Bach Well 56 discharges through a nozzle 58 into the secondary mixture conduits 14. Metering orifices 52 are controlled by a pair of metering rods 60 positioned by a fuel metering control which includes a metering rod carrier 62 and a cam follower 64.

As shown in FIGURE 6, metering rod carrier 62 has an inverted U-shape configuration to fit over a cam follower member 64 and be secured thereto by screws 66 and 68. As viewed in FIGURE 5, member 64 has an arcuate configuration at the top so that the metering rod carrier 62 may be rocked relative to member 64 to vertically position the metering rods 60 within the metering orifices 52.

As viewed in FIGURE 2, adjusting screws 66 and 68 extend through slots 70 and 72 in metering rod carrier 62 so that the carrier 62 may be adjusted longitudinally with respect to member 64 to angularly position metering rods 60 within metering orifices 52.

As shown in FIGURE 5, a metering cam 74 is secured to the air valve shaft 24 between the secondary mixture conduits 14. An economy scheduling portion 76 and a power scheduling portion 78 are located on diametrically opposed portions of cam 74. Cam follower member 64 is bifurcated about cam 74 and has an economy follower 80 and a power follower 82. Cam follower member 64 has an arm 84 extending to a piston 86 biased by a spring 88. Piston 86 is subjected through passages 90, 92 and 94 to intake manifold vacuum which exists in mixture conduits 14 downstream of throttle valves 18.

Operation When the engine is running, manifold vacuum will pull piston 86 upwardly and cam follower member 64 will be rotated by its own Weight about a pivot 96 so that the economy follower 80 contacts the economy scheduling portion 76 of metering cam 74. As throttle 18 is opened, vacuum will be communicated to the underside of air valves 22 to cause them to open. Return spring 28 is calibrated so that a substantially constant pressure drop exists across air valves 22 whenever they are opened.

As air valves 22 open, valve shaft 24 and metering cam 74 rotate to raise cam follower member 64 and metering rod carrier 62. Metering :rods 60 will be withdrawn from metering orifices 52. Fuel will flow from [fuel bowl 44 through metering orifices 52, passages 54, main wells 56, nozzles 58 to .the secondary mixture conduits 14. The rate of fuel flow to the mixture conduits 14 is determined by the position of metering rods 60 within metering orifices 52.

'An enriched air-fuel mixture is required when the manifold vacuum downstream of throttles 18 drops to a predetermined point. Spring 88 is calibrated so that at this time, it will overcome the slight vacuum force on piston 86 and push piston 86 downwardly -to rotate cam member 64 clockwise about pivot 96. Cam follower 82 will contact power scheduling portion 78 of metering cam 74 to raise metering rods 60 an additional amount and provide additional fuel to the secondary mixture conduits 14.

It will be appreciated that, although this air and fuel metering mechanism has been described and illustrated as used in a carburetor, the mechanism can be easily adapted for use in other types of fuel systems. This invention is advantageous in all these systems because it al lows fuel metering control through a single mechanism operated by an air valve during engine operation in both the economy and power ranges.

I claim:

1. A carburetor comprising a pair of mixture conduits, a rotatable shaft extending through said conduits, an air valve in each conduit secured to said shaft, means controlling said air valves whereby their Iotative position is determined by and is a measure of air flow through said conduits, a throttle valve in each conduit downstream of said air valve, a fuel bowl, a pair of fuel passages extending from the bottom of said bowl to said conduits, fuel metering orifices in said fuel passages at the juncture with the bottom of said bowl, a vertically reciprocable metering rod in each of said orifices, a cam secured to and rotatable with said shaft between said conduits, said cam having diametrically opposed economy and power scheduling portions, the srotative position of said cam being a measure of the rate of air flow through said mixture conduits, and a fuel metering control including a cam follower portion bifurcated into economy and power following arms respectively disposed on diametrically opposite sides of said cam adjacent said economy and power scheduling portions of said cam, a carrier portion supported by said cam follower portion, said metering rods being suspended from said carrier portion, means mounting said fuel metering control for pivotal movement in a vertical plane, said economy follower arm of said cam follower portion being biased into contact with said economy scheduling portion of said cam, and means responsive to low vacuum in said conduits downstream of said throttle valves and adapted to bias said power follower arm of said cam follower portion against said power scheduling portion of said cam whereby rotation of said cam in accordance with a change in the rate of air flow through said conduits pivots said fuel metering control to reciprocate said metering rods within said orifices and provide the desired economy and power air-fuel mixture ratios.

2. The carburetor of claim 1 which further includes means for adjusting said carrier portion both longitudinally and vertically with respect to said cam follower portion whereby said metering rods may be properly positioned within said orifices.

3. The carburetor of claim 1 wherein said mixture conduits are secondary mixture conduits and wherein said carburetor further includes a pair of primary mixture conduits.

References Citedby the Examiner UNITED STATES PATENTS 2,390,143 12/1945 Wunsch 261-49 2,445,098 7/1948 Wirth 261-37 2,445,099 7/ 1948 Wirth 26137 2,457,570 12/ 1948 Leibing.

2,499,554 3/ 1950 Wirt'h 261-'37 2,501,060 3/1950 Leibi-ng 73-228 2,523,798 9/ 1950 Winkler 26 139 2,600,368 6/ 1952 Winkler.

2,777,678 1/1957 Udale 26 l-4l 2,991,056 7/ 1961 Shelton 26150 2,996,051 8/ 1961 Mick.

3,053,240 9/ 1962 Mick.

HARRY B. THORNTON, Primary Examiner. RONALD R. WEAVER, Examiner. 

1. A CARBURETOR COMPRISING A PAIR OF MIXTURE CONDUITS, A ROTATABLE SHAFT EXTENDING THROUGH SAID CONDUITS, AN AIR VALVE IN EACH CONDUIT SECURED TO SAID SHAFT, MEANS CONTROLLING SAID AIR VALVES WHEREBY THEIR ROTATIVE POSITION IS DETERMINED BY AND IS A MEASURE OF AIR FLOW THROUGH SAID CONDUITS, A THROTTLE VALVE IN EACH CONDUIT DOWNSTREAM OF SAID AIR VALVE, A FUEL BOWL, A PAIR OF FUEL PASSAGES EXTENDING FROM THE BOTTOM OF SAID BOWL TO SAID CONDUITS, FUEL METERING ORIFICES IN SAID FUEL PASSAGES AT THE JUNCTURE WITH THE BOTTOM OF SAID BOWL, A VERTICALLY RECIPROCABLE METERING ROD IN EACH OF SAID ORIFICES, A CAM SECURED TO AND ROTATABLE WITH SAID SHAFT BETWEEN SAID CONDUITS, SAID CAM HAVING DIAMETERICALLY OPPOSED ECONOMY AND POWER SCHEDULING PORTIONS, THE ROTATIVE POSITION OF SAID CAM BEING A MEASURE OF THE RATE OF AIR FLOW THROUGH SAID MIXTURE CONDUITS, AND A FUEL METERING CONTROL INCLUDING A CAM FOLLOWR PORTION BIFURCATED INTO ECONOMY AND POWER FOLLOWING ARMS RESPECTIVELY DISPOSED ON DIAMETRICALLY OPPOSITE SIDES OF SAID CAM ADJACENT SAID ECONOMY AND POWER SCHEDULING PORTIONS OF SAID CAM, A CARRIER PORTION SUPPORTED BY SAID CAM FOLLOWER PORTION, SAID METERING RODS BEING SUSPENDED FROM SAID CARRIED PORTION, MEANS MOUNTING SAID FUEL METERING CONTROL FOR PIVOTAL MOVEMENT IN A VERTICAL PLANE, SAID ECONOMY FOLLOWER ARM OF SAID CAM FOLLOWER PORTION BEING BIASED INTO CONTACT WITH SAID ECONOMY SCHEDULING PORTION OF SAID CEM, AND MEANS RESPONSIVE TO LOW VACUUM IN SAID CONDUITS DOWNSTREAM OF SAID THROTTLE VALVES AND ADAPTED TO BIAS SAID POWER FOLLOWER ARM OF SAID CAM FOLLOWER PORTION AGANIST SAID POWER SCHEDULING PORTION OF SAID CAM WHEREBY ROTATION OF SAID CAM IN ACCORDANCE WITH A CHANGE IN THE RATE OF AIR FLOW THROUGH SAID CONDUITS PIVOTS SAID FUEL METERING CONTROL TO RECIPROCATE SAID METERING RODS WITHIN SAID ORIFICES AND PROVIDE THE DESIRED ECONOMY AND POWER AIR-FUEL MIXTURE RATIOS. 